The most relevant trends in the optical networking area are the increase in the network capacity and the increase in transmission reach. A higher network capacity is obtained by increasing the channel rate, known as TDM (time division multiplexing), and/or by increasing the channel density, known as WDM (wavelength division multiplexing).
Advances in transmitter and receiver design, evolution of optical amplification, employment of distributed Raman amplification combined with various dispersion compensation techniques, new encoding and modulation techniques, digital wrapper technology, etc., enabled the installation of ultra-long reach networks, where regeneration of the signal is effected at 3,000 km or more.
However, current WDM networks use point-to-point connectivity, which means that all channels are OEO (optical-to-electrical-to-optical) converted at each node. In addition, the pt-pt network requires duplication of equipment for protection/restoration in case of fault. As a result, the configuration of a typical node of a point-to-point network is very complex. On the other hand, OEO conversion at all intermediate nodes is not necessary in the majority of cases, since the modern ULR techniques allow optical signals to travel distances greater than the distance between two or more successive nodes without regeneration. Thus, important cost savings may be obtained by eliminating the unnecessary OEO conversion equipment.
There is a need to reduce the cost of the network nodes by maximizing the distance traveled by the signals in optical format, to take advantage of the emerging ULR techniques and to provide a more efficient use of the network equipment.
Furthermore, scaling-up or/and providing new services in a point-to-point network requires very complex network engineering and planning involving extensive simulation and testing. Currently, the waiting time for a new optical service in point-point networks is over 120 days.
There is a need to break the wavelength engineering bottleneck currently constraining the engineering-to-provisioning ratio, and for wavelengths to became available as a network resource automatically deployable across the network. There is also a need to minimize the number of wavelengths that are deployed while avoiding the color clash effect for optical signals having different wavelengths and sharing a single fiber, for efficient use of all network resources.